With the development of touch control technologies and mobile terminal technologies, more and more mobile terminals achieve man-machine interactions by means of touch control. At present, touch screens employed by the mobile terminals mainly include capacitive touch screens and resistive touch screens, wherein the capacitive touch screens are popular among more and more people with better definition, light transmittance and touch feeling.
A capacitive touch screen is composed of a touch sensor and a touch controller. The touch sensor is composed of a plurality of capacitor nodes. When the touch screen is touched, the capacitance value of a corresponding capacitor node varies. Upon detecting the variation, the touch controller may determine a corresponding touch position. For detection on whether the capacitive touch screen is touched, a capacitance value of all the capacitors on the touch screen when being not touched in a frame needs to be acquired as a reference, that is, a stable reference value. After the stable reference value is determined, a touch state may be judged by comparing the capacitance values of the capacitor nodes at the current time with a reference. Therefore, acquisition of the capacitance value of the capacitor node when the touch screen is not touched as the reference is very important in touch control by using the touch screen.
However, in the practical process of determining the reference of the above capacitor node, due to various causes, for example, variations of environment, the capacitance value of the touch screen varies (for example, an original capacitance value of the capacitor node becomes smaller or becomes greater due to temperature rise or temperature reduction and the like). In this case, a present reference needs to be maintained, to adapt to new conditions. For example, the current reference is re-determined based on the original capacitance value of the capacitor node, or the current capacitance value of the capacitor node is used as the current reference or other adaptation manners or the like are used.
However, no matter which manner is used, the determined capacitance value may still be inaccurate. Therefore, how to determine the reference of the touch screen as accurately as possible is a technical problem to be urgently solved.